As better described in French patent No. 2,670,440, this vehicle comprises a powertrain with a thermal engine including a speed variation device and an electric machine connected to an electric battery. This system also comprises two clutches, a first clutch between the thermal engine and the electric machine, and a second clutch between the electric machine and the speed variation device.
Thus, when the vehicle is to be driven with a high torque over a wide speed range while limiting exhaust gas and noise generation, as in an urban site, the electric machine is preferably used for driving this vehicle.
On the other hand, the thermal engine is used for driving this vehicle for uses where a high driving power and a wide operating range are required.
Although satisfactory, this drive system however involves some significant drawbacks.
In fact, when only the electric machine is used to drive the vehicle, sufficient torque is required therefrom, not only to drive the vehicle, but also to overcome all the resistances (inertia, friction, . . . ) inherent in the vehicle and in the speed variation device.
A hybrid vehicle has also been proposed, notably in U.S. Pat. No. 6,344,008, wherein part of the speed variation transmission device comprises an epicyclic gear train with a crown, a sun gear and a planet gear carrier.
In this type of epicyclic gear train, it is difficult to control the direction of rotation of the various elements, which can go against the desired one. This leads to parasitic stresses and load torques that prejudice the smooth running of this epicyclic gear.
The present invention aims to overcome the aforementioned drawbacks by means of a simple and reliable speed variation device allowing the required speed level to be obtained.